Impact tool



March 12, 1957 H. c. R EYNQLDS 2,784,819

IMPACT TOOL Filed Oct. 11, 1954 2 She ets-Sheet l INVENTOR HAROLD C. REYNOLDS BY WW4.

HIS ATTORNEY March 12, 1957 H. c. REYNOLDS IMPACT TOOL.

2 Sheets-Sheet 2 Filed Oct. 11, 1954 INVENTOR HAROLD C. REYNOL ms ATTORNEY United States Patent IMPACT TOOL Harold C. Reynolds, Athens, Pa., assignor to Ingersoll- Rand Company, New York, N. Y., a corporation of New Jersey Application October 11, 1954, Serial No. 461,306

Claims. (Cl. 192-305) This invention relates to impact tools, and more par ticularly to a hammer driving and declutching mechanism for portable impact tools of the type having a motor driven hammer adapted to deliver to an anvil a constant turning force at low torque loads and at high torque loads, a series of high velocity rotary blows, for rotating nuts, bolts or similar work pieces.

In tools of this type, and especially tools used in assembly line operations, it is highly desirable that the tool be simple in design and capable of operating relatively trouble free for long periods of time.

It is accordingly one object of this invention to provide a driving and declutching mechanism of relatively simple and compact design.

Another object is to provide such a connection which is sufliciently compact to be adapted for use in small impact tools and also of such design that it can develop suflicient disengaging force to be adapted for use in relatively large tools.

Further objects will become obvious from the following description and drawings in which;

Figure 1 is a vertical elevation, partly in section, showing a preferred embodiment of the invention of the mechanism adapted to an impact tool.

Figure 2 is a cross-sectional view taken through Fig. 1 along the line 2-2 looking in the direction of the arrows, and

Figs. 3 and 4 are similar to Fig. 2 but show different operative positions of the hammer relative to the anvil.

Referring to Fig. l of the drawings, a preferred form of the impact tool is shown as comprising, in general, a casing 8 housing a motor driven carrier 9 on which is eccentrically pivoted a hammer 10 having a longitudinal jaw, or lug, 16 arranged to strike a series of blows on a jaw 18 on an anvil 12 to rotate a workpiece 14.

The connection between the motor and the carrier 9 includes a driving element 20 positively engaged to the motor 15 and pivotally connected by member 34 to bear against a cam element 22 on the hammer 10 such that there is a force tending constantly to rotate the carrier 9 and hammer 10 about the anvil 12 and to rock the hammer 10 about its eccentric axis 24 out of engagement with the anvil 12. Thus the driver 20--cam 22 connection serves not only as a driver, but additionally as a means for disengaging the hammer 10 from the anvil 12 immediately after a hammer blow is struck so that the carrier 9 is free to be quickly accelerated to a high velocity prior to the hammer 10 striking the next blow. During this free movement of the carrier 9, cam means 26, 28 on the hammer 10 and anvil 12, respectively, positively rock the hammer 10 about its axis 24 into position to engage the anvil.

Referring now in greater detail to the construction of the impact tool shown only by way of illustrating the use of the invention, the motor 15 is of the type that can be loaded until it stalls without damage to the motor.

This type of motor, such as an air motor, is required because during the impacting cycle of tightening opera: tion, the hammer 10, and hence the motor 15, is often brought to a complete halt at the time of impact of the hammer 10 on the anvil 12, and then accelerated to maximum speed prior to the next blow.

Connected, as by splines 30, to the motor shaft 32 is the driver 20 which includes apair of arms arranged to exert a driving and rocking force on the cam 22 integral with the hammer 10. The arms of the driver are in the form of pins 34 and 36 with their ends fitted in sockets,

i or recesses, 38 and 40 in the driver wings 42 and cam 22, respectively. The recesses 38 and 40 are located such that the longitudinal axis (line B, Fig. 3) of eachpin 34 and 36 is at all times outside (relative to the car rier axis) of the hammer axis 24. Inasmuch as the axis 24 of the hammer is also the axis of the cam 22, any force exerted by. the driver 20 on the cam 22 tends to rock the hammer 10 about the axis 24 in the same direction as the direction of rotation of the carrier 9 to disengage the hammer from the anvil.

The magnitude of the disengaging force for any given motor torque can be varied, withinlimits set by other factors, by moving the location of the recesses 38 and 40 so as to vary the perpendicular distance (A in Fig. 3) from the longitudinal axis B of pin 34 to the cam axis 24 or the perpendicular distance (C in Fig. 3') from the axis B to the axis 44 of the carrier and driver. The ratio of these distances determines the cam leverage exerted by the driver on the hammer. For example, where th distance C is three times that of distance A, then a driver force of 3 pounds exerts a cam force of 1 pound tending to rotate the hammer.

It is to be noted that the size of any driver is limited by the size of the casing 8 and accordingly the length of the lever arms, especially arm A, is also limited. Tests have shown, however, that the driver arrangement disclosed is not only adaptable to small impact tools, but that a sufiicient pivotal force can be developed by this driver to move the relatively heavy hammer of a large impact tool.

In addition to exerting a cam force tending to rock the hammer 10 about its axis 24, the driver 20 also drives, or rotates, the hammer about a more central axisthe axis 44 of the carrier. In furtherance to this end, the hammer 10 is mounted on and rotated with the carrier 9. The carrier 9 comprises a pair of end plates 46 and 48 rotatably mounted on the driver 20 and anvil stem 50, respectively, and has a semicircular connecting wall portion 52 having its center located approximately 180 from the center of the relatively heavy jaw portion of the hammer 10 such that the wall serves additionally as a counterweight.

The hammer 10 which is roughly tubular in shape is eccentrically mounted on a pin 54 extending through the end plates 46 and 48. The bore 56 of the hammer shown is the same radius for approximately Z50 degrees. The remaining are 58 of degrees is of somewhat greater radius and with a different center point, thus a pair of longitudinal shoulders, or jaws, 16 and 61) are provided for engagement with the anvil jaws 18 and 62, respectively. The shape of the periphery of the bore arc portion 58 and, within relatively broad limits, the lengths of the arcs are relatively unimportant from the tool operation standpoint, however, the jaws 18 and 62 are formed such that the striking jaw is positioned substantially radial to the axis of the anvil 12 at the time of the blow (see Fig. 2). The depth of the jaws 16 and 60 are such that when the hammer is pivoted by the driver, the contacting hammer jaw moves clear of the contacted anvil jaw (see jaws 16 and 18-Fig. 3).

The anvil 12 is in the form of a cylinder with a recess Patented Mar. 12, 1957 64 at the rearward end in which the motor shaft 32 is piloted, whereas the forward end, or stem portion 50 extends through the front end of the casing 8 and is adapted to fit a socket 66 or similar element for connection with a workpiece. Located along the rearward end portion of the anvil 12 and positioned within the hammer bore 56 is a radially extending lug 68 having a radius only slightly less than the radius of the 250 degrees portion of the bore 56 and being approximately 105 degrees in length. Thus lug 68 provides the two shoulders, or anvil jaws, 18 and*62 the faces of'which are substantially radial to the anvil axis so that when a hammer blow is struck the contacting surfaces-e. g., see jaws 16' and 18 in Fig. 2' are in parallelism and full surface contact is obtained. Of course these jaw surfaces may be inclined slightly from the radial to obtain a slight declutching or clutching efiect where such elfect is deemed desirable.

The outer periphery of the lug 68 serves additionally as the cam means 28 which cooperates with the cam means, or surface, 26 of the hammer bore 56 to rock the hammer about the pin 54 and place a hammer jaw in full alignment with an anvil jaw prior to a hammer blow.

Reviewing briefly the operation of the impact tool and assuming the tool has been mounted on a workpiece, such as the nut 14 shown in Fig. 1, and assuming further that the hammer is rotated clockwise, as viewed in Fig. 2, the various elements of the tool will take the positions shown in Fig. 2 with the hammer shoulder 16 contacting the anvil shoulder 18 and the pin 34 exerting a driving force on the cam 22. During any period When there is very little resistance to rotation of the anvil 12, as when the nut 14 is being threaded along the bolt 70 and prior to seating against a plate 74, the camming force exerted by the driver pin 34 on cam 22 tending to pivot the hammer out of engagement with the. anvil is normally not sufficient to overcoming the frictional force between the an- I vil and hammer jaws l8 and 16, respectively. Accordingly, the hammer and anvil 12 will remain engaged so that the nut 14 is rotated constantly until the resistance to rotation increases above some predetermined value.

When the resistance to rotation of the anvil exceeds said predetermined value, the driver arm 34 acting on the cam 22 will rock the hammer about its axis 24 into the position shown in Fig. 3 with the hammer shoulder 16 moved out of alignment with the anvil shoulder 18. The motor will then quickly accelerate the carrier 9 through 360 degrees such that the hammer is moving at substantially the maximum speed of rotation of the motor prior to striking the next hammer blow. During this relatively free rotation of the carrier 9, the hammer cam surface 26 comes in contact with the anvil cam surface 28 (see Fig. 4) and the hammer is gradually and positively pivotedabout its axis 24 against the camming force exerted by the driver arm 34 and cam 22 sothat the hammer shoulder 16 is moved into alignment with the anvil shoulder 18 immediately prior to impact between these two shoulders. I i

The hammer 10 in striking a high velocity blow on the anvil 12, rotates the workpiece 14 until, again, the camming force exerted by the arm 34 and cam overcome the frictional force between the hammer and anvil shoulders 16 and 18, respectively, so that the hammer It) is rocked about its eccentric axis 24 and out of engagement with the anvil. It is to be understood that the time of disengagement of the hammer from the anvil will vary somewhat, depending upon the degree of tightness of the work. For example, when the work is relatively loose,

the hammer will remain engaged with the anvil and to tate through several degrees prior to disengaging, whereas when the work is relatively tight there is a tendency for the hammer to rebound after a blow is struck, and the hammer will be disengaged from-the anvil during such rebound.

The operation of the tool in the counterclockwise direction is identical with clockwise operation, except, of course, impacting now occurs between the jaws 60 and 62 and the driving and declutching camming force is exerted by the arm 36 on the cam 22.

While I have shown and described a specific form of my invention, it is to be understood that various changes and modifications may be made without departing from the spirit of the invention as set forth in the appended claims.

I claim:

l. A hammer driving and declutching mechanism for an impact tool having a driving motor and a hammer adapted to be rotated about a central axis to deliver a series of blows to an anvil and adapted to be pivoted about an eccentric axis for clutching and declutching movement with respect to such anvil, comprising a driving element adapted to be connected for rotation by said motor and having a lever arm, a cam element immovably mounted on the hammer and having a lever arm, and a member having pivotal connections with the end portions of said arms for transmitting force therebetween tending to move the hammer out of engagement with the anvil after a hammer blow is struck.

2. A hammer declutching mechanism as claimed in claim 1 in which said member constitutes the sole driving connection between the hammer and motor for ro- ,tatiug the hammer about its central axis.

3. A hammer declutching mechanism as claimed in claim 2 in which said pivotal connections are located such that the direction of force exerted by said member on the cam element tends constantly to pivot the hammer about its eccentric axis in the same direction as the direction of rotation of the hammer about its central axis.

4. A hammer driving mechanism as claimed in claim 2 in which the pivotal connection on the cam is located adjacent the eccentric axis of the hammer and :the pivotal connection on the driving element is located such that the longitudinal axis of said member lies outside, relative to the central axis, of the eccentric axis of the hammer.

5. A declutching mechanism as claimed in claim 4 in which said member is in the form of a pin having its endlocated in recesses in said lever arms.

6. A hammer driving and declutching mechanism for a rotary impact tool having a motor, an anvil, a rotatable carrier, a hammer mounted on the carrier for movement about a pivotal axis to alternately engage and disengage with the anvil to deliver a series of hammer blows thereto, and means for positively moving the hammer into position to engage the anvil prior to such harnmer blow, comprising a driving element connected to be rotated by the motor, a cam element immovably -,mounted on the hammer, and a member having pivotal connections with the driving and cam elements for transmitting force therebetween tending to rotate thehammer to strike the anvil, the point of connection of said memher with the cam element being displaced from the pivotal axis of the hammer such that the member exerts a force direction of rotation of the hammer about the anvil for delivering hammer blows thereto.

8. The combination with an impact tool having a motor, an anvil, and a hammer adapted to be rotated about a central axis to deliver a series of blows to the anvil andadapted to be p ivotedabout an eccentric axisto move into andout of engaging position with the anvil, of a driving clement connected to be rotated by the motor and having a radially extending wing, a cam element immovably mounted on the hammer, and a member having pivotal connections with said wing and cam element for the point of connection of said member with the wing being displaced radially of the central axis of the hammer and the point of connection of said member with the cam element being displaced circumferentially of the hammer pivotal axis such that the member transmits a force constantly tending to rotate the hammer about its central axis to strike the anvil and constantly tending to move the hammer about its eccentric axis out of engagement with the anvil after the hammer blow is struck.

9. The combination claimed in claim 8 in which the pivotal connections of said member are such that the direction of force exerted by said member on the cam element tends to pivot the hammer about its eccentric axis in the same direction as the direction of rotation of the driving element.

10. The combination claimed in claim 8 in which the driving element is provided with a pair of oppositely radially extending wings with recesses located at the ends thereof, the cam element is located with its axis coinciding with the eccentric axis of the hammer with recesses in the cam on the opposite sides of said eccentric axis, and members are provided on each side of said central axis with their ends positioned in said recesses to connect each wing with the corresponding sides of the cam.

References Cited in the file of this patent UNITED STATES PATENTS 

